4:00 PM - 6:00 PM
▲ [17p-PB07-13] Growth and Self-Separation of HVPE GaN on Sapphire Substrates Using Patterned Graphene buffer Layer
Keywords:Gallium Nitride, Graphene, Hydride vapour phase epitaxy
Due to the absence of a native substrate, high-quality free-standing gallium nitride (GaN) is often obtained by growing a thick layer (up to several hundred micrometers) of GaN on a foreign substrate such as sapphire by hydride vapor phase epitaxy (HVPE). However, the mismatch in thermal expansion coefficients between GaN and sapphire makes it very challenging to scale up this technique at a reasonable cost. As the diameter of the wafer increases, the wafer bowing becomes worse and the wafers often break during cooling, which dramatically reduces the yield. Even if the wafer survives the cooling step, it can still break during the laser lift-off step. After the lift-off, the wafer is still severely bowed because of the residual stress inside free-standing GaN.One way to overcome this issue is to naturally induce self-separation by utilizing the stress during the cooling step. Specifically, we propose to insert a 2D material between sapphire and GaN to weaken the interfacial bonding force between sapphire and GaN. This can lead to elastic strain relaxation without generating defects. The weakened interface also means GaN can be more easily separated from sapphire and can self-separate. Graphene was chosen as a 2D buffer layer for this work. The graphene surface was patterned in an acidic atmosphere after transferring the graphene layer onto the sapphire substrate through a transfer method. Self-separation during HVPE growth was achieved with 300-μm thick GaN. The crystallinity and optical properties of GaN films produced by self-separation were evaluated. The advantages of the patterned 2D material on the crystallinity of GaN and the mechanism of self-separation were reviewed.This work was supported by the Technology development Program(S3056775) funded by the Ministry of SMEs and Startups(MSS, Korea)